1. Field of the Invention
This invention relates to polyurethane foams suitable for contact with vinyl films and to processes for their manufacture. More specifically, this invention relates to a process for the manufacture of polyurethane foams which exhibit a reduced tendency to stain vinyl films with which they are in contact.
2. Description of the Prior Art
The use of molded polyurethane products having vinyl films adhered thereto has increased dramatically in recent years. These products now commonly appear in automotive interiors as dashboards, door linings and arm rests as well as in in many furniture-related applications.
While these materials perform excellently in these applications, they possess a deficiency which has been widely recognized. Specifically, the staining of the vinyl film has been found to be caused by components of the polyurethane to which it is adhered. This staining problem is especially prevalent in environments wherein elevated temperatures exist, such as in automobile interiors, since the severity of the staining appears to vary directly with temperature.
Amine catalysts present in the polyurethane foams have been found to be responsible for vinyl staining. Various solutions to this problem have been proposed. For instance, JA59-191743 discloses the use of the reaction product of dimethylaminepropylamine and carbonic acid as a catalyst for use in the manufacture of polyurethane. The use of this catalyst is stated to reduce odor and vinyl staining relative to the use of standard triethylene amine catalysts. EP 176,013 discloses the use of specific aminoalkylurea catalysts in the manufacture of polyurethanes. Use of these catalysts is also said to reduce odor and the staining of vinyl films adhered thereto. The references allegedly accomplish this reduction in odor and vinyl staining through the use of relatively high molecular weight amine catalysts. Due to their high molecular weight, these amine catalysts are unable to readily migrate through a polyurethane foam and thus, their propensity to produce odors and stain vinyl films. However, when subjected to elevated temperatures as are commonly encountered in automobile interiors, these compounds migrate within a foam to some degree Therefore, there continues to be a need for alternate means to control vinyl staining by polyurethane compositions.
It has now been found that other components of polyurethane compositions are also responsible for vinyl staining. Specifically, it has been found that amine containing cross-linking compounds, as described herein, incorporated in a polyurethane composition will also promote vinyl staining.